Field of Invention
The present invention relates to a porous metal mold for a wet pulp molding process and a method of using the same, and more particularly, to a porous metal mold which is made by powder metallurgy and is used for forming a wet paper-shape product/semi-finished product by thermo-compression.
Description of Prior Art
Recently, for environmental protection, paper-shape package material has been widely applied for various products, such as electronic devices or food containers. In a conventional wet pulp paper-shaping process which mainly comprises a dredging step and a compression-forming step, the implementations of the dredging step and compression-forming step must adopt a set of mold assembly (such as an upper mold and a lower mold) so as to form the finished paper-shape products. Conventionally, the mold assembly is applied with traditional aluminum-casted molds and a layer of metal mesh additionally overlapped on forming surfaces of the aluminum-casted molds. In the dredging step, the aluminum-casted molds are used to dredge up the paper fibers from a slurry tank containing a paper slurry, thereby keeping the paper fibers on the metal mesh. In the compression-forming step, a vacuum pump device liquid-communicated with the bottom of the aluminum-casted mold is used to absorb part of water off of the paper fibers on the metal mesh, in order to leave the paper fibers on the metal mesh to form the wet pulp.
However, the metal mesh is usually welded directly onto the forming surfaces of the aluminum-casted molds. During the compression-forming step, the metal mesh is continuously punched by the absorbing air flows and the compression applied between the molds, such that the metal mesh is easily drawn to thorns, cracked, broken, apart from the molds, or even deformed. This results in extremely shorting the life time of the aluminum-casted molds. After repeating the compression-forming step for several times, an artificial repair or a replacement of the metal mesh is necessary. Besides, grids and/or the welding point of the metal mesh are easily branded onto the surface of the wet paper-shape product made by the metal mesh, to form screen printings affecting the appearance and plainness of the products after.
Furthermore, the traditional metal mesh does not only need to manually weave the metal mesh in complication and wasting time to form a simple arc shape, but also limit the shape of other new products. Also, the aluminum-casted molds with the metal mesh need to form a plurality of through holes distributed around the outer surface of the molds, for exhausting the water and moisture contained in the paper fibers above the metal mesh to dry. In order to prevent machining process of forming the through holes on the aluminum-casted molds from being implemented difficult after the formation process of the whole molds, the aluminum-casted molds need to punch the through holes on the outer surfaces of the aluminum-casted molds by a mechanical drilling method, after the aluminum-casted molds has been casted, time and effort is needed. The distance between every two through holes would be limited by the mechanical drilling method so that the density of arranging the through holes is lower, and then by performing a machining process (cutting or milling), the finial-required contour of the aluminum-casted molds is shaped. This would invoke the mold development risk increased. During the operation of cutting or milling, the scraps can very easily choke the through holes, which is difficult to clean manually. Hence, how to create a new mold design and mold-manufacturing art which can lower the manufacturing cost and enhances the economical profit is required for development.